JP2008516272A - System and method for analyzing the shape of a photomask - Google Patents

Abstract

  After the simulated shape (106) is generated, the simulated shape (106) may be modified to generate the predicted shape (108). The predicted resulting shape (108) is a modified shape (as input for the photomask (52) to image the resist layer of the photomask blank used to make the photomask (52). 102) includes prediction of the shape that will be formed in the pattern layer (58) of the photomask (52). In other words, the predicted resulting shape (108) is the pattern layer (58) if the etching process is performed over the area of the pattern layer (58) defined by the simulated shape (106). Including prediction of the shape that will be formed.

Description

Cross-reference to related applications This application is a U.S. patent entitled "Systems and Methods for Predicting Photometrics Using Simulation" by Kent Nakagawa et al. The priority of provisional application 60 / 615,881 is claimed.

  The present disclosure relates generally to the manufacture of integrated circuits, and more particularly to systems and methods for analyzing the shape of photomask geometries.

  Integrated circuit devices typically include various circuit components such as transistors, resistors and capacitors. These integrated circuit components are formed by forming specific shapes on a semiconductor wafer (eg, a silicon wafer) using various integrated circuit manufacturing techniques including, for example, lithographic techniques using one or more photomasks. It may be produced.

  The photomask itself may be formed from a photomask blank using various lithographic processes. A mask pattern file defining one or more shapes to be formed in the absorber layer of the photomask blank is a pattern such as a laser system, an electron beam system, or an x-ray lithography system. It may be used as input by a pattern-imaging tool. The pattern imaging tool may be used to expose a portion of the resist layer that is formed over the absorber layer of the photomask blank that corresponds to the shape defined by the mask pattern file.

  However, the accuracy of the shape actually imaged on the resist layer (as compared to the shape defined by the mask pattern file) may be limited by the specific pattern imaging tool used. . For example, if an electron beam or laser is used to transfer the pattern to the resist layer, the sharpness or sharpness of the particular shape imaged on the resist layer is limited by the width of the electron beam or laser beam used There is a possibility that. Thus, due to distortions due to the physical limitations of the imaging tool, certain shapes defined by the mask pattern file may not be transferred to the photomask resist layer with sufficient or desired accuracy. is there.

  FIG. 1 shows an exemplary shape 10 defined by the mask pattern file and a corresponding shape 12 that is actually imaged on the resist layer of the photomask, where the difference between shape 10 and shape 12 is used Due to the physical limitations of the pattern imaging tool used. As shown in FIG. 1, due to the limitations of the pattern imaging tool, the corners of the imaged shape 12 are rounded. The degree of corner-rounding is related to the pattern imaging tool used, such as the electron beam or laser width used.

  After the pattern defined by the mask pattern file is imaged on the resist layer of the photomask, the exposed area of the resist layer is developed and etched to create a pattern in the resist layer. The portion of the underlying photomask blank absorber layer (eg, the exposed area) that is not covered by the resist is then etched, and then the undeveloped portion of the resist layer is the desired pattern ( Or may be removed to create an approximation of the desired pattern). During etching of the exposed area of the absorbing layer, additional portions of the absorbing layer beyond the edge of the exposed area may also be etched. Such additional etching may be referred to as “overetching”. Thus, if the etching process is performed on an exposed area of the absorbing layer having a particular shape, the actual portion of the absorbing layer removed by the etching process will have a different, eg, more comprehensive, shape. May have. For example, if the overetch is relatively uniform around the perimeter of the shape of the portion of the absorber layer being etched, the shape of the actual portion of the absorber layer removed by the etching process is exposed to the opaque layer. May have a periphery that is uniformly offset from the shape of the area.

  Following the example shown in FIG. 1, FIG. 2 shows an exemplary shape 12 imaged on the resist layer of the photomask blank and formed in the absorber layer of the photomask blank by the etching process described above. An exemplary shape 14 is shown. As shown in FIG. 2, the periphery of the shape 14 actually formed in the absorbing layer is offset from the periphery of the shape 12 imaged on the resist layer due to the effect of overetching. This overetching can be caused by a variety of factors, such as undercutting the resist layer during the wet etch process, or erosion of the resist layer during the dry etch process.

  FIG. 3 illustrates the exemplary effect of overetching in the corner regions 16 of the shapes 10, 12 and 14 shown in FIGS. The offset due to the effect of overetching is generally uniform in the direction perpendicular to the edge of the shape 12 at each point along the edge of the shape 12 as indicated by the uniform length arrow 18. May have a large distance, D. As shown, the arrows 18 each extend along the edge of the shape 12 in a direction perpendicular to the respective location. Since the change in end position is perpendicular to each point at the end of shape 12, the effect is a change in curvature at the corners of shape 12 and other non-linear portions. Accordingly, the curvature of the shape 14 in the corner region 16 is different from the curvature of the shape 12 in the corner 16. In particular, the curvature of the corner 20 inside the shape 14 may be less sharp (or less sharp) and the curvature of the corner 22 outside the shape 14 may be sharper (or sharper).

  The absorption layer of the photomask, which may be referred to as a patterned layer, may include one or more components having a shape corresponding to an integrated circuit (IC) component to be formed on a semiconductor wafer. Good. During the lithographic process, a pattern layer containing the shape of the IC component is transferred onto the surface of the semiconductor wafer to form the corresponding IC component. These IC components include, but are not limited to, resistors, transistors, capacitors, interconnects, biases, and metal lines, for example.

  In some cases, it is important or critical for the proper operation of the resulting IC that the particular IC component is precisely and / or accurately formed. It would therefore be desirable to be able to predict the resulting shape that would actually be formed in the photomask absorber layer (or pattern layer) based on the specific shape defined in the mask pattern file. In particular, such prediction is (1) the difference between the shape defined in the mask pattern file and the corresponding shape actually imaged on the resist layer of the photomask blank, and the pattern used Differences that may be caused by physical limitations of the imaging tool, and (2) the shape imaged on the resist layer of the photomask and the shape actually formed on the absorption layer (or pattern layer) of the photomask It would be desirable to take into account both of the differences that can be attributed to over-etching.

wrap up

  The teachings of the present disclosure have substantially reduced or eliminated the disadvantages and problems associated with predicting and / or analyzing the shape of a photomask.

  In certain embodiments, a method for analyzing the shape of a photomask is provided. An original shape to be formed with the absorption layer of the photomask blank is received. The original shape may be modified to produce a modified shape that is offset from the original shape in at least one direction. A simulation may be performed based on the modified shape to determine the simulated shape, in which case the simulated shape is used as an input for imaging the modified shape onto the resist layer. If so, it is a simulated prediction of the shape that will be drawn into the photomask blank resist layer. The simulated shape may then be modified to determine the predicted original shape, where the predicted original shape is the absorption layer defined by the shape simulated by the etching process. When executed on the area, it is a prediction of the shape that will be formed by the absorption layer of the photomask blank.

  In another embodiment, a system for analyzing the shape of a photomask is provided. The system may include a computer system having a processor and a computer readable medium interfaced to the computer system. The computer readable medium, when executed by the processor, receives the original shape to be formed in the absorption layer of the photomask blank, changes the original shape to produce a changed shape, and the changed shape Contains a shape that is offset in at least one direction from the original shape and performs a simulation based on the modified shape to determine the simulated shape. Simulated to produce the predicted original shape, including simulated predictions of the shape that would be drawn into the photomask blank resist layer when used as input to image the layer The shape is changed and the predicted original shape is It may include software operable including prediction of shape to be formed on the absorber layer of the photomask blank if made on the area of the defined absorption layer by emulates shape.

  One advantage of at least some embodiments of the present disclosure is that the absorbing layer of the photomask blank to form the photomask pattern layer when a particular shape is used as input for the formation of the pattern layer A system and method is provided for predicting the resulting shape that will be formed. The shape defined by the mask pattern file can be used to predict the actual pattern that will be formed in the pattern layer if the mask pattern file is used as input. It may be simulated before it is actually formed. Based on the results of such simulation, the mask pattern file may be adjusted until an appropriate predicted actual pattern is determined. This is an undesirable production photomask due to the difference between the shape defined by the mask pattern file used to generate the pattern layer and the shape actually formed in the pattern layer. ) Can reduce or eliminate the possibility of forming a pattern layer on top of each other (for example, these differences may be due to dimensional limitations and / or over-etching inherent in the tool used to generate the pattern layer). Due to factors such as impact). Thus, the time and expense associated with forming undesirable photomasks (which may need to be discarded) can be reduced or eliminated. In some embodiments, the simulation may be performed using a computer system.

  All or some of these technical advantages may or may not exist in various embodiments of the present disclosure. Other technical advantages will be readily apparent to one skilled in the art from the following description, as well as the accompanying drawing figures and claims.

  A more complete and thorough understanding of the present embodiments and their advantages can be obtained by reference to the following description, taken in conjunction with the accompanying drawings, wherein like reference numerals indicate like features.

  Various embodiments of the present disclosure and their advantages are best understood by referring to FIGS. 4-10, wherein like numerals are used to indicate like and corresponding parts.

  FIG. 4 illustrates a cross-sectional view of an exemplary photomask assembly 50 according to some embodiments of the present disclosure. The photomask assembly 50 may include a pellicle assembly 54 that is mounted on the photomask 52. The substrate 56 and pattern layer 58 may form a photomask 52, also known as a mask or reticle, which may have a variety of sizes and shapes including, but not limited to, circular, rectangular, and square. The photomask 52 may also be a one-time master, a 5 inch reticle, a 6 inch reticle, a 9 inch reticle, or any other suitable that may be used to project an image of a circuit pattern onto a semiconductor wafer. It can be any of a variety of photomask types, including but not limited to size reticles. The photomask 52 may further be a binary mask, a phase shift mask (PSM) (eg, an alternating approach phase shift mask, also known as a Levenson-type mask), an optical proximity correction (OPC) mask, or a lithography system. Any other type of mask suitable for use may be used.

A pattern layer 58 of the photomask 52 is formed on the surface 57 of the substrate 56 that projects a pattern onto the surface of the semiconductor wafer (not explicitly shown) when exposed to electromagnetic energy in the lithography system. May be. The substrate 56 may be quartz, synthetic quartz, fused silica, magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), or at least 75 percent (75%) of incident light having a wavelength between about 10 nm and about 450 nm. It may be a transparent material such as any other suitable material that passes through. In one alternative embodiment, the substrate 56 is reflective such as silicon or any other suitable material that reflects more than about 50 percent (50%) of incident light having a wavelength between about 10 nm and 450 nm. It may be a material.

  The pattern layer 58 may be, for example, chromium, chromium nitride, metal nitride oxycarbo (eg, MOCN, where M is chromium, cobalt, iron, zinc, molybdenum, niobium, tantalum, titanium, tungsten, aluminum, magnesium, and silicon. Or any other suitable that absorbs electromagnetic energy having wavelengths in the ultraviolet (UV) range, deep ultraviolet (DUV) range, vacuum ultraviolet (VUV) range, and extreme ultraviolet (EUV) range. A metal material such as a simple material may be used. In one alternative embodiment, the patterned layer 58 is partially transmissive material having a transmission from about 1 percent (1%) to about 30 percent (30%) in the UV, DUV, VUV and EUV ranges, for example It may be molybdenum silicide (MoSi).

  Frame 60 and pellicle film 62 may form pellicle assembly 54. Frame 60 is typically formed of alumite, but may alternatively be stainless steel, plastic, or other suitable material that does not decompose or outgas when exposed to electromagnetic energy in a lithography system. . The pellicle film 62 is made of, for example, nitrocellulose, acetylcellulose, E.I. I. Amorphous fluoropolymers such as TEFLON (registered trademark) manufactured by du Pont de Nemours and Company or CYTOP (registered trademark) manufactured by Asahi Glass, or others that are transparent to wavelengths in the UV, DUV, EUV and / or VUV range A thin film film formed of a material such as a suitable film may be used. Pellicle film 62 may be made by conventional techniques such as, for example, rotational molding.

  The pellicle film 62 can protect the photomask 52 from contaminants such as dust particles by ensuring that the contaminants remain a defined distance away from the photomask 52. This can be particularly important in lithography systems. During the lithography process, photomask assembly 50 may be exposed to electromagnetic energy generated by a radiant energy source in the lithography system. The electromagnetic energy may include light of various wavelengths, for example, light at wavelengths between about I and G rays of mercury arc lamps, or DUV, VUV or EUV light. In implementation, the pellicle film 62 may be designed such that a large percentage of electromagnetic energy can pass through it. Contaminants collected on the pellicle film 62 may be out of focus on the surface of the wafer being processed, so the image exposed on the wafer should be sharp. A pellicle film 62 formed in accordance with the teachings of the present disclosure can be fully used with all types of electromagnetic energy and is not limited to the light waves described in this application.

  Photomask 52 may be formed from a photomask blank using standard lithographic processes. In a lithographic process, a mask pattern file that includes data for the pattern layer 58 may be generated from a mask layout file. The mask layout file may define one or more shapes that may include, for example, polygons or other shapes representing various IC portions such as transistors, resistors, capacitors, biases, and wires. The shape defined by the mask layout file may further represent various layers of the integrated circuit when fabricated on a semiconductor wafer. For example, the transistor may be formed on a semiconductor wafer having a diffusion layer and a polysilicon layer. Thus, the mask layout file may define one or more polygons drawn on the diffusion layer and one or more polygons drawn on the polysilicon layer. Each layer of polygons may be converted to a mask pattern file representing one layer of the integrated circuit. Each mask pattern file may be used to generate a photomask for a particular layer. In some embodiments, the mask pattern file defines multiple layers of an integrated circuit such that a photomask may be used to image features from multiple layers on the surface of a semiconductor wafer. May be.

  The desired pattern of the pattern layer 58 can be obtained by using a mask pattern file as input and a photomask blank using a laser, electron beam, x-ray lithography system, or other suitable pattern imaging tool. An image may be formed on the resist layer. The imaged portion of the resist layer may be referred to as the “exposed” area. In one embodiment, the laser lithography system uses an argon-ion laser that emits light having a wavelength of about 364 nm. In other implementations, the laser lithography system uses a laser that emits light of a wavelength from about 150 nm to about 300 nm.

  As mentioned above, the accuracy of imaging the shape defined by one or more mask pattern files onto the resist layer may be limited by the particular pattern imaging tool used. For example, if an electron beam or laser is used to transfer the pattern to the resist layer, the sharpness or sharpness of the particular shape that may be imaged on the resist layer is the width of the electron beam or laser beam used May be limited. Thus, due to distortions due to the physical limitations of the imaging tool, the particular shape in the pattern defined by the one or more mask pattern files is sufficient for the photomask with sufficient or desired accuracy. 52 may not be transferred to the resist layer.

  After the pattern defined by one or more mask pattern files is imaged on the resist layer, the exposed area of the resist layer is developed and etched away to create a pattern in the resist layer. May be. The portion of the underlying pattern layer 58 that is not coated with resist may then be etched, and then a desired pattern (or at least an approximation of the desired pattern) is created in the pattern layer 58 overlying the substrate 56. In order to do this, the undeveloped portion of the resist layer may be removed. In some cases, additional portions beyond the edge of the exposed area may also be etched, which may be referred to as “overetch”.

  Defined by the mask pattern file so that the actual pattern formed in the pattern layer 58 can be predicted to eliminate distortions due to tool physical limitations and / or over-etching effects. The pattern (or portion thereof) may be simulated before the pattern layer 58 is actually formed on the photomask 52. Based on the simulation results, one or more mask pattern files may be adjusted until an appropriate predicted actual pattern is determined. This is used to create such a patterned layer 58 (eg, due to factors such as dimensional limitations inherent in the equipment used to create the patterned layer 58, the effects of overetching, etc.) Due to the difference between the shape in the pattern defined by the one or more mask layout files and the resulting shape of such a pattern layer 58, the pattern layer 58 on the photomask 52 is undesirable. The possibility of forming can be reduced or eliminated.

  FIGS. 5A-5C are exemplary methods for predicting the resulting shape formed in the pattern layer 58 of the photomask 52 based on a particular shape defined by a mask pattern file in accordance with certain embodiments of the present disclosure. Indicates. FIG. 5A shows the desired shape 100 defined by the mask pattern file. The desired shape 100 is a shape intended to be formed from one or more semiconductor wafers and may correspond to one or more components of an integrated circuit to be formed from the semiconductor wafer.

  Desired shape 100 may be modified by a particular offset extending around the desired shape 100 to produce a modified shape 102. The offset width or distance, D, may be completely or at least substantially uniform around the desired shape 100. In some embodiments, the offset width or distance, D, may be used (or expected to be used) to form a shape in the pattern layer 58 during the formation of the photomask 52. ) May be determined based on the expected distance of overetching associated with the etching process. For example, if a specific etch process is used to form the patterned layer 58 with the photomask 52, it is known that a 30 nm overetch will occur, to produce a modified shape 102 D An offset of = 30 nm may be used. As shown in FIG. 5A, one or more particular features 104 (eg, relatively small features) of the desired shape 100 may be offset due to an offset that extends around the modified shape 102. It may be lost when the modified shape 102 is generated.

  After generating a modified shape 102 having an offset of distance D from the desired shape 100, the modified shape 102 is determined to determine a simulated shape 106, as shown in FIG. 5B. Based on the above, a computerized simulation may be performed. The simulated shape 106 is a photomask 52 when the modified shape 102 is used as input by a pattern imaging tool such as a laser imaging tool, an electron beam imaging tool, or an x-ray lithography system, for example. Represents a simulated prediction of the shape to be drawn above. For example, the simulation may attempt to predict corner rounding and other effects associated with imaging a particular shape (in this case, the modified shape 102). The simulation may include one or more suitable algorithms or modeling functions, such as one or more Gaussian functions or equations. In some embodiments, the size of the Gaussian spot is adjusted to accommodate a particular imaging tool, such as an ALTA laser writer (eg, ALTA 4000 tool) or a JEOL electron beam tool (e-beam tool). May be. The simulation may be performed or facilitated using any suitable software application, such as CALIBRE ™ modeling software available from Mentor Graphics Corporation ™.

  After the simulated shape 106 is generated, the simulated shape 106 may be modified to generate the predicted resulting shape 108. The predicted resulting shape 108 is processed by the photomask 52 using the modified shape 102 as an input to image the resist layer of the photomask blank used to make the photomask 52. If so, it includes prediction of the shape that will be formed by the pattern layer 58 of the photomask 52. In other words, the predicted resulting shape 108 will be formed with the pattern layer 58 if the etching process is performed over the area of the pattern layer 58 defined by the simulated shape 106. Includes shape prediction. Thus, the predicted resulting shape 108 can take into account the shape offset expected to be caused by over-etching when the simulated shape 106 is etched into the pattern layer 58. As shown in FIG. 5C, the offset that may extend around the simulated shape 106 may have a uniform width, or distance, D.

  As shown in FIG. 5C, the straight line portion of the shape 108 as the predicted result (more specifically, the straight line portion not adjacent to the corner region of the desired shape 100) is the corresponding straight line of the desired shape 100. It may substantially match the part. This is because the straight portion of the modified shape 102 is offset inward from the desired shape 100 by a distance D, and the straight portion of the simulated shape 104 (or at least the portion not adjacent to the corner region) is simulated. The corresponding straight portion of the modified shape 102 to be substantially matched, and the predicted straight portion of the shape 108 is offset outwardly from the simulated shape 104 by a distance D. Arise from. Accordingly, the offset toward the inside of the distance D and the offset toward the outside may essentially cancel each other.

  FIG. 6 shows a comparison between the predicted resulting shape 108 generated according to the method shown in FIGS. 5A-5C and a conventional predicted shape. Similar to the predicted resulting shape 108, the traditional predicted shape 120 uses the modified shape 102 as an input for the photomask 52 to image the resist layer of the photomask 52 (as described above). When processed in this manner, it represents a predicted shape that will be formed by the pattern layer 58 of the photomask 52. However, the conventional predicted shape 120 is different from the predicted resulting shape 108, such as by applying one or more Gaussian functions or equations to the desired shape 100, and so on. Generated using a model or other known technique.

  In at least some cases, the predicted resulting shape 108 is formed in the pattern layer 58 of the photomask 52 when the modified shape 102 is used as an input to image the resist layer of the photomask 52. A substantially accurate simulated approximation of the shape to be done. In at least some cases, the predicted resulting shape 108 will be formed in the pattern layer 58 of the photomask 52 over a previously simulated shape, such as the conventional predicted shape 120, for example. Is a more accurate approximation of the actual resulting shape.

  FIG. 7 is a detailed view of the first corner region 122 of the comparison of the predicted resulting shape 108 shown in FIG. 6 with the conventional predicted shape 120. As shown in FIG. 7, the curved portion of the conventional predicted shape 120 of the corner region 122 is at least substantially symmetric with respect to the inner corner 124 and the outer corner 126. In contrast, the predicted curved portion of the shape 108 of the corner region 122 is asymmetric with respect to the inner corner 124 and the outer corner 126. In particular, the curvature of the inner corner 124 of the predicted shape 108 is less sharp (or less sharp), while the curvature of the outer corner 124 of the predicted result 108 is conventional. It is sharper (or sharper) than the predicted shape 120 symmetry curve. In some cases, this asymmetric curve may be formed in the pattern layer 58 of the photomask 52 by etching the pattern layer 58 as compared to a previously simulated shape, such as the conventional predicted shape 120, for example. More accurately approximate the actual shape curve.

  FIG. 8 is a detailed view of the second corner region 130 of the comparison of the predicted result shape 108 shown in FIG. 6 with the conventional predicted shape 120. As shown in FIG. 8, the curve portion of the predicted resulting shape 108 of the corner region 130 is less sharp (or less sharp) than the curve portion of the conventional predicted shape 120 of the corner region 130. ). In some cases, the predicted curved portion of the shape 108 of the corner region 130 may be caused by etching the pattern layer 58 relative to a previously simulated shape, such as the conventional predicted shape 120, for example. The actual shape curve formed in the 52 pattern layers 58 is approximated more accurately.

  FIG. 9 illustrates the resulting shape (eg, discussed herein) that is formed in the pattern layer 58 of the photomask 52 based on the specific shape defined by the mask pattern file, in accordance with certain embodiments of the present disclosure. 1 illustrates an exemplary system 200 for predicting a predicted result 108). System 200 may include a processor 202 and a memory 204 that may be operable to store a simulation software application 206 and / or a mask pattern file 208. The simulation software application 206 is discussed herein for predicting the shape formed in the pattern layer of the photomask, such as the method of generating the predicted resulting shape 108 discussed herein with respect to FIGS. Any software suitable to perform any or all of the functions may be included. The mask pattern file 208 is one or more that includes data defining the shape to be formed in the pattern layer of the photomask and / or data defining such a shape for simulation or other testing. Any computer-readable file may be included.

  The processor 202 may perform all or any of the methods discussed herein for predicting the shape formed in the pattern layer of the photomask, such as the method of generating the predicted resulting shape 108 discussed herein with respect to FIGS. Any suitable processor or processors that execute simulation software application 206 or other computer instructions may be included to implement the portion. For example, the processor 202 may use the actual photomask pattern layer when such a shape is used as an input to form a pattern layer (eg, when such a shape is used as an input by an imaging tool). Simulation software that simulates or otherwise processes the shapes defined by one or more mask pattern files 208 to predict the resulting shapes that will actually be formed Any suitable processor that executes application 206 may be included.

  In some embodiments, processor 202 may be a central processing unit (CPU) or other microprocessor, and may be any suitable number of cooperating processors. Examples of the memory 204 include one or more random access memories (RAM), read only memory (ROM), dynamic random access memory (DRAM), fast cycle RAM (FCRAM), static RAM ( SRAM, field programmable gate array (FPGA), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), microcontroller, or microprocessor One or more devices suitable for facilitating execution of software application 206 or other computer instructions may be used.

  FIG. 10 illustrates a method of forming a patterned layer 58 on the photomask 52 according to one embodiment of the present disclosure. At step 300, a mask pattern file 208 defining an original shape (eg, desired shape 100) may be received. In step 302, the original shape may be modified with a particular offset extending around (and inward) the desired shape 100 to produce a modified shape (eg, modified shape 102). Good. As discussed above, the offset distance is based on the expected distance of overetching associated with the etching process that may be used to shape the pattern layer 58 during formation of the photomask 52. May be determined.

  After generating the modified shape offset from the original shape, in step 304, a computerized based on the modified shape is used to determine a simulated shape (eg, simulated shape 106). A simulation may be performed. The simulated shape may include a simulated prediction of the shape that will be drawn on the photomask 52 if the modified shape is used as input by the pattern imaging tool. For example, such a simulation may attempt to predict corner rounding and / or other effects associated with imaging the altered shape. As discussed above, the simulation may include one or more of any suitable algorithm or modeling function, such as one or more Gaussian functions or equations.

  After the simulated shape is generated, the simulated shape uses the modified shape as an input to image the resist layer of the photomask blank used to create the photomask 52. If the photomask 52 has been processed, it may be modified in step 306 to create a prediction of the shape that will be formed in the pattern layer 58 of the photomask 52 (eg, the shape as a predicted result). 108). In other words, the predicted resulting shape is formed in the pattern layer 58 if the etching process is performed on the area of the pattern layer 58 defined by the simulated shape determined in step 304. It may include prediction of the shape that will be different. Thus, the predicted resulting shape can take into account the expected shape offset that would result from over-etching if the simulated shape was etched into the pattern layer 58.

  At step 308, it may be determined whether the predicted resulting shape determined at step 306 is sufficient. For example, it may be determined whether a particular feature is cut off or misacceptably improperly shaped, for example due to rounded corners. If the predicted resulting shape determined in step 306 is insufficient, at least a portion of the original shape defined in the mask pattern file 208 is the predicted result determined in step 306. It may be modified in step 310 based on the shape of For example, if the predicted resulting shape indicates that a particular feature is cut off or unacceptably inappropriate (eg due to rounded corners), the original shape It may be modified accordingly. Steps 302-308 are then repeated to determine the predicted resulting shape in response to the modified shape determined in step 310. This process may be repeated iteratively until it is determined in step 308 that the predicted resulting shape is sufficient.

  After it has been determined that the predicted resulting shape is sufficient in step 308 (if one or more modifications have been made as discussed above) An original shape corresponding to the shape or a modified original shape may be used to form the pattern layer 58 of the photomask 52. In this discussion, this original shape or modified original shape that corresponds to a well-predicted resulting shape may be referred to as a “selected shape”. In step 312, the selected shape may be modified by a particular offset that extends around (and inwards) the selected shape to produce a modified selected shape. Further, the offset distance may be determined based on the expected distance of the overetch associated with the etching process. Thus, if the selected shape is the original shape defined in the mask pattern file 208 (eg, if the original shape was not modified in step 310), the changed selected shape is It may be the same as the changed shape determined at 302.

  In step 314, the imaging process may be performed using the modified selected shape as an input to expose an area of the resist layer of the photomask blank used to create photomask 52. Good. In some cases, the shape of the exposed area may be substantially similar to the simulated shape determined in step 304. At step 316, the exposed area of the resist layer may be developed and removed to uncover the area of the absorber layer of the underlying photomask blank. The shape of the area from which the absorber layer coating has been removed may be substantially similar to the shape exposed by the imaging process in step 314. In step 318, one or more etching processes may be performed to remove the area of the absorber layer (eg, in the area where the absorber layer coating has been removed) to form the patterned layer 58 of the photomask 52. It may be carried out on the area from which the coating of the absorber layer has been removed (through the open area of the upper resist layer). Due to the effects of over-etching, the actual area of the absorbent layer removed by the etching process may be larger than the area of the absorbent layer that was decoated in step 316. In some cases, the shape of the actual area of the absorber layer removed by the etching process may be substantially similar to the predicted resulting shape determined to be sufficient at step 308.

  Although the disclosed embodiments have been described in detail, it should be understood that various changes, substitutions and modifications can be made to the embodiments without departing from their spirit and scope. It is.

FIG. 5 shows exemplary shapes defined in a mask pattern file and corresponding shapes actually imaged on a resist layer of a photomask blank using the mask pattern file as input. Exemplary shapes defined in the mask pattern file, corresponding shapes actually imaged on the resist layer as shown in FIG. 1, and photomasks after the etching process has been performed It is a figure which shows the illustrative shape actually formed with the absorption layer of the blank. FIG. 3 shows an exemplary effect of overetching at specific corners of the shape shown in FIGS. 1 and 2. 2 is a cross-sectional view of an exemplary photomask assembly formed in accordance with some embodiments of the present disclosure. FIG. FIG. 3 illustrates an exemplary method for predicting a resulting shape used to form a photomask pattern layer based on a specific shape defined by a mask pattern file, in accordance with certain embodiments of the present disclosure. It is. FIG. 3 illustrates an exemplary method for predicting a resulting shape used to form a photomask pattern layer based on a specific shape defined by a mask pattern file, in accordance with certain embodiments of the present disclosure. It is. FIG. 3 illustrates an exemplary method for predicting a resulting shape used to form a photomask pattern layer based on a specific shape defined by a mask pattern file, in accordance with certain embodiments of the present disclosure. It is. FIG. 6 shows a comparison of the predicted resulting shape generated according to the method shown in FIGS. 5A-5C with a conventional predicted shape. FIG. 7 is a detailed view of a first corner region of a comparison between the predicted resulting shape shown in FIG. 6 and a conventional predicted shape. FIG. 7 is a detailed view of a second corner region of a comparison of the predicted resulting shape shown in FIG. 6 with a conventional predicted shape. FIG. 3 illustrates an exemplary system for predicting a resulting shape used to form a photomask pattern layer based on a specific shape defined by a mask pattern file, in accordance with certain embodiments of the present disclosure. It is. 3 is a flow diagram of a method for forming a patterned layer on a photomask according to one embodiment of the present disclosure.

Claims (21)

A method for analyzing the shape of a photomask,
Receiving the original shape to be formed on the absorption layer of the photomask blank,
Modifying the original shape to generate a modified shape, the modified shape including a shape offset from the original shape in at least one direction;
A simulation is performed based on the modified shape to determine a simulated shape, and the simulated shape is used when the modified shape is used as an input to image a resist layer. Including a simulated prediction of the shape to be imaged on the resist layer of the photomask blank; and
The simulated shape is modified to produce a predicted original shape, and the predicted original shape is measured on an area of the absorbing layer defined by the simulated shape by an etching process. Including predicting the shape that would otherwise be formed in the absorber layer of the photomask blank. The original shape includes a first periphery;
The modified shape includes a second periphery, the second periphery being identified from the first periphery of the original shape such that the second periphery is located inside the first periphery. Offset by distance,
The method of claim 1.   The method of claim 2, wherein the second perimeter is offset from the first perimeter of the original shape by the specified distance across the first perimeter.   The specific distance of the offset between the second periphery and the first periphery is determined based on a known distance of overetching associated with the etching process used during photomask formation. The method of claim 2, wherein:   The method of claim 1, wherein performing the simulation based on the modified shape to determine the simulated shape comprises using one or more Gaussian functions.   Performing the simulation based on the modified shape to determine the simulated shape is a shape associated with imaging the modified shape onto the resist layer of the photomask blank. The method of claim 1, comprising approximating a strain of   The method of claim 1, wherein altering the simulated shape to generate the predicted original shape comprises generating a shape that is offset in at least one direction from the simulated shape. The method described.   The simulated shape includes a first perimeter, the predicted original shape includes a second perimeter, and the second perimeter is such that the first perimeter is located inside the second perimeter. The method of claim 7, wherein the method is offset by a specific distance from the first periphery of the simulated shape.   9. The method of claim 8, wherein the second periphery of the predicted original shape is offset by the specific distance from the first periphery of the simulated shape across the first periphery. .   The specific distance of the offset between the second periphery and the first periphery is an over-etching knowledge associated with the etching process used during processing of the absorber layer of the photomask blank. The method of claim 8, wherein the method is determined based on the distance being measured. The original shape includes a first periphery;
The modified shape includes a second periphery, the second periphery being identified from the first periphery of the original shape such that the second periphery is located inside the first periphery. Offset by distance,
The simulated shape includes a third shape;
The predicted original shape includes a fourth periphery, and the fourth periphery is the third shape of the simulated shape such that the third periphery is located inside the fourth periphery. Offset by a certain distance from the periphery,
The method of claim 7. The original shape includes specific portions having an inner corner and an outer corner, the outer corner being symmetric with respect to the inner corner;
The predicted original shape includes a curved portion corresponding to the particular portion of the original shape, the curved portion of the predicted original shape being asymmetric with respect to the inner corner and the outer corner;
The method of claim 1. The original shape includes a first straight portion;
The predicted original shape corresponds to the first straight portion of the original shape and includes a second straight portion at substantially the same position as the first straight portion;
The method of claim 1.   The method of claim 1, further comprising modifying at least a portion of the original shape based on the determined predicted original shape.   The method of claim 1, wherein the absorbing layer of the photomask blank is substantially opaque.   The simulated shape is a simulated shape that will be imaged onto the resist layer of the photomask blank if the modified shape is used as input by a pattern imaging tool. The method of claim 1, comprising prediction.   The predicted original shape is formed in the absorbing layer of the photomask blank when the modified shape is used as an input to form a pattern layer on the absorbing layer of the photomask blank. The method of claim 1, comprising predicting a shape to be. A method for analyzing the shape of a photomask,
Receiving data defining the original shape to be formed on the absorption layer of the photomask blank;
Automatically processing the received data to generate a modified shape based on the original shape, the modified shape including a shape offset in at least one direction from the original shape;
Perform a computerized simulation based on the modified shape to determine a simulated shape, and the simulated shape is used as an input for imaging the modified shape on the resist layer. Including a simulated prediction of the shape that will be imaged onto the resist layer of the photomask blank and automatically generating the simulated shape to produce the predicted original shape. The predicted original shape is formed in the absorption layer of the photomask blank if an etching process is performed on the area of the absorption layer defined by the simulated shape. Including predicting the shape that will be. A method for forming a photomask, comprising:
Receiving the original shape to be formed on the absorption layer of the photomask blank,
Modifying the original shape to generate a modified shape, the modified shape comprising a shape offset in at least one direction from the original shape;
A simulation is performed based on the modified shape to determine a simulated shape, and the simulated shape is used when the modified shape is used as an input to image the resist layer. Including a simulated prediction of the shape that will be drawn into the photomask blank resist layer;
Modifying the simulated shape to produce a predicted original shape, and the predicted original shape is an etching process performed on the area of the absorbing layer defined by the simulated shape Including prediction of the shape that would be formed in the absorber layer of the photomask blank if
Modifying at least a portion of the original shape based on the generated predicted original shape;
Using the modified original shape as input to expose one or more portions of the resist layer of the photomask blank;
Developing one or more exposed portions of the resist layer of the photomask blank to remove a coating on one or more portions of the absorbing layer of the photomask blank, and a pattern layer Performing an etching process that removes the stripped portion of the absorber layer of the photomask blank to form a mask. A photomask including a photomask pattern formed in an absorption layer, wherein at least a part of the photomask pattern is
Receiving the original shape to be formed on the absorption layer of the photomask blank,
Modifying the original shape to generate a modified shape, the modified shape comprising a shape offset in at least one direction from the original shape;
A simulation is performed based on the modified shape to determine a simulated shape, and the simulation is performed when the modified shape is used as an input to image the resist layer. Including a simulated prediction of the shape that will be drawn into the blank resist layer,
Modifying the simulated shape to generate a predicted original shape, and the predicted original shape is an etching process performed on the area of the absorbing layer defined by the simulated shape Including prediction of the shape that would be formed in the absorber layer of the photomask blank if
Modifying at least a portion of the original shape based on the generated predicted original shape;
Modifying the modified original shape to generate a modified modified shape, wherein the modified modified shape includes a shape that is offset in at least one direction from the modified shape;
Using the modified modified original shape as an input to expose one or more portions of the resist layer of the photomask blank;
Developing the one or more exposed portions of the resist layer of the photomask blank to remove a coating on one or more portions of the absorbing layer of the photomask blank, and a pattern A photomask formed by performing an etching process that removes the removed portion of the one or more coatings of the absorber layer of the photomask blank to form a layer. A system for analyzing the shape of a photomask, comprising: a computer system having a processor; and a computer readable medium coupled to the computer system, wherein the computer readable medium is executed by the processor If
Receive the original shape to be formed on the absorption layer of the photomask blank,
Modifying the original shape to produce a modified shape, the modified shape comprising a shape offset in at least one direction from the original shape;
A simulation is performed based on the modified shape to determine a simulated shape, and the simulated shape is used when the modified shape is used as an input to image the resist layer. Including a simulated prediction of the shape that will be drawn into the resist layer of the photomask blank;
Modifying the simulated shape to produce a predicted original shape, and the predicted original shape is an etching process performed on the area of the absorbing layer defined by the simulated shape A system comprising software operable to include a prediction of a shape that would be formed in the absorber layer of the photomask blank if done.

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